A system for operating a dual fuel injection engine is described in U.S. Pat. No. 7,281,517. This patent describes a supplying fuel to a cylinder of an engine using a port fuel injector and a direct fuel injector. The port fuel injector timing and direct fuel injector timing can be varied to change the total amount of fuel injected to the cylinder. The system appears to use separate fuel pumps and injector drivers to enable individual control of direct and port fuel injectors so that the fraction of fuel that the port or direct injector provides to the cylinder can be varied with engine operating conditions.
The above-mentioned system can also have several disadvantages. For example, adding double the number of fuel injectors and fuel pumps can more than double the injection system cost as compared to a comparable port only fuel injection system. Further, additional wires and control circuitry are required to control and operate the two types of fuel injectors. Further still, the additional wiring and control circuitry can increase the space and weight necessary to implement the described system.
The inventors herein have recognized the above-mentioned disadvantages and have developed a system and method that offers substantial improvements.